Out of the many stimuli that bombard us, only a small fraction ever makes it into our conscious perception. What distinguishes those that are selected for conscious access from those that remain subliminal? And what separates the normal human brain, which is capable of conscious access, from that of patients in coma or vegetative state, who no longer seem to gain conscious access to any information? Using brain-imaging tools, particularly magneto-encephalography, I will show recent tests of the global neuronal workspace theory of consciousness, which suggest that conscious access relates to a late and global ignition in a distributed circuit involving prefrontal and parietal nodes. The signatures of consciousness that we observe in the normal brain are now starting to be translated into the clinic.